Since aromatic polycarbonate resins are tough resins having not only excellent impact resistance and electrical properties but also good dimensional stability, they are being utilized as a useful engineering plastic. However, the resins are defective, for example, in that they have poor moldability due to the high melt viscosity and their solvent resistance is so poor that contact with aromatic solvents or gasoline causes the resins to develop cracks. These defects have restricted the application range for the aromatic polycarbonate resins.
In order to improve such insufficient properties, it has been proposed to add various kinds of resins to aromatic polycarbonate resins. For example, JP-B-36-14035 (the term "JP-B" as used herein means an "examined Japanese patent publication") proposes addition of poly(ethylene terephthalate) to improve moldability (flowability) and solvent resistance, and U.S. Pat. No. 3,218,372 proposes addition of a poly(alkylene terephthalate) for the same purpose. In this method in which the poly(alkylene terephthalate) is added to improve solvent resistance, the larger the amount of the poly(alkylene terephthalate) added, the more the solvent resistance is improved. However, the increased amount of poly(alkylene terephthalate) results in molded articles which not only tend to have sink marks, etc., but also have poor impact resistance and heat resistance.
It has been proposed to further add a thermoplastic elastomeric polymer to improve impact resistance (e.g., JP-B-55-9435, JP-B-62-37671). Known as such elastomeric polymers are methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate-acrylate-styrene copolymer (MAS), methyl methacrylate-acrylate-butadiene-styrene copolymer (MABS), acrylic ester-based core-shell copolymers, polyester elastomers, and other elastomers.
Further, for the purpose of improving heat resistance, preventing sink mark occurrence, lowering coefficient of linear expansion, and improving strength and stiffness, it has also been attempted to add glass fibers, carbon fibers, and other various kinds of inorganic fillers or reinforcements.
As a result of the improvements described above, compositions comprising an aromatic polycarbonate resin, a thermoplastic polyester resin, a thermoplastic elastomeric polymer, and a reinforcement are being extensively used in exterior automotive parts such as door handles, side moldings, wheel covers, fender panels, and garnishes, because the compositions have excellent solvent resistance, impact resistance, strength, and stiffness and have low coefficient of linear expansion.
However, these compositions have had a problem that they are insufficient in surface appearance, particularly surface smoothness, so that they are poor in image clarity after coating. Although fibrous reinforcements such as glass fibers and carbon fibers are especially useful for improving strength and stiffness and lowering coefficient of linear expansion and, particularly, the glass fibers are widely used as such a reinforcement because of their low cost, use of the conventional glass fibers has been disadvantageous in that the glass fiber-reinforced compositions have poor surface smoothness and, hence, satisfactory image clarity cannot be obtained.